A Winthrop man accused of holding up a Dunkin Donuts assisted police in their investigation by leaving his cellphone behind as he fled the scene, officials said.

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Dennis Stack, 41, was arraigned Tuesday in Charlestown District Court on a charge of armed robbery in connection with the Dec. 10 incident.

Boston police were called to the Cambridge Street Dunkin Donuts shortly after noon. The assailant ordered the employee to hand over gift cards and cash, claiming he was armed and threatening kill everyone inside the doughnut shop, police said.

As the man tried to climb over the counter, a customer grabbed him from behind and a brief physical struggle ensued. Stack dropped a tire iron and a white iPhone before fleeing the store with $65 from the register, prosecutors said.

The customer was uninjured and was able to describe the getaway vehicle used by the suspect, as were other customers inside the store.

Officers placed a call to one of the phone numbers that appeared on the phone's screen and spoke with an individual who identified Stack as the phone's owner, prosecutors said.

The Dec. 10 robbery is one of at least four in which Stack is accused. He has also been charged in connection with a Dec. 1 robbery at a Dunkin Donuts in Revere, a Dec. 9 robbery at a Cambridge Street flower shop and an attempted robbery the same day at a Chelsea hair salon that was thwarted when a clerk told him there was no money in her cash drawer.